Cell phone's wifi settings

Hi everyone!
I am new here, and have just spent the last 2 hours signing up and trying to figure out my question on this website and then trying to see where I a supposed to post a new question?
So please forgive me if I am not in the exact right place... hopefully I am close though!
Basically, I am not nearly as knowledgeable as I wish I was, but the internet connection configurational stuff is very confusing for me. But for now,my basic question is this:

Does a cell phone's wifi settings interfere or conflict with data usage or tethering?

(IE., why would I ever want to"turn off" OR "disable" my phone's wifi? Is there a disadvantage to keeping it on permanently, even though where I live I hardly ever (like 20% of the time) get a decent wifi signal? ) If not, then why does the option to turn it off even exist?
I have been all over the internet trying to find out the answer to this!
Also, where on the phone is the internet reception receiver? So that I know what part to be careful not to cover when using, and what part to aim toward my window...
(Btw, I can use my 2 GB/mo. data, but would like to conserve it when possible so I dont run out halfway thru the month)
Thanks so much for any tips!

"Also, where on the phone is the internet reception receiver? So that I know what part to be careful not to cover when using, and what part to aim toward my window..."
To the best of my knowledge, the edges of your phone.